The Impact of Medicaid Expansion on Continuous Enrollment: A Two-State Analysis of All Payer Claims Data
Discussant: Jacob Wallace
In this paper, we assessed the impact of Medicaid expansion under the ACA on continuity of coverage. Using a longitudinal difference-in-difference framework, we compared Colorado, a state that expanded Medicaid, and Utah, a neighboring nonexpansion state, before (2013) and after (2014-2015) the implementation of Medicaid expansion. Our study population consisted of a closed cohort of 349,221 adults ages 18-62 who were enrolled in Medicaid coverage in Colorado and Utah in 2013, prior to expansion. Enrollment data from 2013-2015 were obtained from all payer claims databases from both states. Unique person identifiers enabled patient tracking across different types of insurance.
The primary outcomes were enrollment duration measured by the total number of months of Medicaid coverage per calendar year and coverage disruption rates defined as disenrollment or a gap in coverage greater than 31 days. Secondary outcomes measured transitions from Medicaid to commercial insurance. Individual-level baseline covariates included age, sex, the Elixhauser comorbidity index, and prior use of health services measured by the number of ED visits, inpatient stays, and outpatient visits during 2013. Area-level covariates included the proportion of the geographic area that identified as White, Black, Hispanic, and Asian, unemployment, uninsured and poverty rates, median household income, educational attainment, and the proportion of residents in urban versus rural areas.
Following expansion, Medicaid enrollees in Colorado gained an additional two months of coverage over two years of follow-up and were 16 percentage points less likely to experience a coverage disruption in a given year compared to concurrent trends observed for enrollees in Utah, a bordering state that did not expand Medicaid. Insurance gains were driven by reductions in longer periods without coverage as opposed to reductions in shorter gaps.
Our difference-in-difference estimates suggest less insurance churn in Colorado than prior national studies predicted. Medicaid expansion appears to be an effective strategy to improve continuity of coverage in the program. These findings have implications for states considering or actively implementing Medicaid expansion. One such state is Utah, where residents recently passed a ballot initiative to expand Medicaid and those tasked with enacting the program may face legislative challenges.